The snippet that filters the filtered set is
A
var t=new FilteredSet(s, {function(s) {return !(x instanceof Set);});
B
var t=new FilteredSet{function(s) {return !(x instanceof Set);});
C
var t=new FilteredSet(s, {function(s) {return (x instanceof Set);});
D
var t=new FilteredSet(s, {function(s) {return x;});
Correct Answer: var t=new FilteredSet(s, {function(s) {return !(x instanceof Set);});